arcpy.Describe(lyr).FIDSet failure?

I have writen a quick code just to improve my arcpy. The code uses a list of letters and then zooms around a California counties layer based on if their name contains each letter. However, it fails with 'i', 'v', and 'n'. 'W' and 'x' are the only letters it should bounce back. I am not sure why it does not detect a selection with 'i', 'v', and 'n'. The code is run in ArcMap through a toolbox. The code:

arcpy.Describe(countylyr).FIDSetuse:len([r[0] for r in arcpy.da.SearchCursor(countylyr. ["OID@"])])

I would think that the line:

if arcpy.Describe(countylyr).FIDSet:

would always evaluate as true (and execute the code indented underneath it), since you are not explicitly looking to see if the .fidset property actually retuned a string of selected OIDs or just a blank string (it returns a semicolon delimited list of selected OIDs as I recall, otherwise just a blank string... For example '1;2;3;4' vs. just '' if no selection... it does not evaluate to None however (at least in v10.1).